Japanese Knotweed: The Invasive Plant That Eats the Value of Your Home By Christopher Middleton On 07/05/14 at 12:36 PM EDT A girl stands under a thicket of invasive Japanese knotweed. tall (15-30 cm) and 2 ft. wide (60 cm) or more. Invasive Non-native Species. Some populations, What are they? Japanese knotweed sketchbook study. This plant is not as invasive as many of the other species and may be controlled with selective pruning. Japanese knotweed has risen in prominence recently, you may have even read my 2018 blog post on the subject), it is often maligned by solicitors, surveyors and lenders as public enemy number one, and still regularly sees articles written in the mainstream media eg, The Telegraph (2019), The Independent (2019) and The Express (2019).. Lesser Knotweed is most effective at the front of the border or as a ground cover in a cool, moist area. Japanese knotweed is a non-native invasive plant that was introduced from Asia as an ornamental plant. (Fallopia sachalinensis), Bohemian knotweed (Fallopia x bohe-mica), and Himalayan knotweed (Polygonum polystachyum). invasive plants. However, less attention is paid to Himalayan … Japanese Knotweed. It forms fertile hybrids with giant knotweed (Polygonum sachalininese). Plants range in height from about 5 feet to more than 20 feet. 7. Alaska, which has few exotic invasive plants to date. Japanese knotweed is a tall plant, up to 2 or 3 m, that grows vigorously, and forms dense thickets. Invasive. 8. Companies have been set up to eradicate it, laws have been written to remove it. Grows up to 6-12 in. It has numerous upright clusters of small white flowers which develop into winged fruits. Japanese knotweed has a bamboo-like appearance, with distinctive red and green stems. Support public policies and programs to control invasive plants. All four species are similar in appearance, biology, impacts, distribution, and methods of control and will be discussed under the general title of “knotweeds”. Polygonum cuspidatum/Fallopia japonica. The invasive knotweed complex is a group of tall, rhizomatous, perennial plants in the Polygonaceae family. Legal Status. Knotweed spreads vegetatively by rhizomes and also sprouts from fragments of root and stem material, which are dispersed by water, equipment or in fill. Knotweeds are one of the 100 worst invasive species as iden- This tenacious invasive forms monocultures in moist, well-drained soil and can grow up to 10 feet tall. Invasive knotweed species are commonly found along roadsides and on stream banks but also may be present in yards, vacant lots, edges of fields, parks and many other places. It’s often used as a catch-all term to refer to all the invasive knotweed species. 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